Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $59.55   3.335%   $61.536   $61.54   $61.55   $61.50  
  Purchase #2 $69.72   4.353%   $72.7549   $72.75   $72.75   $72.80  
  Purchase #3 $54.34   4.315%   $56.6848   $56.68   $56.70   $56.70  
  Purchase #4 $76.64   10.863%   $84.9654   $84.97   $84.95   $85.00  
  Purchase #5 $16.46   4.674%   $17.2293   $17.23   $17.25   $17.20  
  Purchase #6 $203.37   5.684%   $214.9296   $214.93   $214.95   $214.90  
  Purchase #7 $105.86   13.727%   $120.3914   $120.39   $120.40   $120.40  
  7 purchase totals = $585.94       $628.4914   $628.49   $628.55   $628.50